The present invention relates to an agent for the removal of turbidity in bio-logical samples, particularly serum or plasma samples.
Turbidity typically occurs in plasma or serum samples (lipemic samples) that have an increased content of triglyceride-rich lipoprotein particles, e.g. chylomicrons.
It is particularly necessary to use agents for the removal of turbidity in order to perform photometric analysis of lipemic samples in chemical or clinical diagnosis. If the component to be analysed absorbs at a wavelength corresponding to the absorbing wavelength of the triglycerides causing the turbidity, correct photometric analysis of the component in question will be difficult if not impossible. This applies especially when the concentration of the component to be determined is very low such as, for example, when the analyte is Cell Reactive Protein (CRP).
A common example of a photometric procedure in which the interference of turbidity must be excluded is the assay of CRP. This assay uses anti-human CRP antibodies that specifically react with the CRP in the sample to form insoluble aggregates. The assay is initiated by the addition of the antibodies and the increase in CRP-antibody-aggregates is measured photometrically at 340 nm. The triglycerides in lipemic samples also absorb at this wavelength, so there is a risk of overlapping extinction signals.
To resolve this problem with lipemic samples, several agents are known in the prior art that can be added in order to remove turbidity. In this connection, U.S. Pat. No. 4,708,939 discloses an agent comprising a polyethoxylated triglyceride and a secondary n-alkane sulphonate in an aqueous solution. This known agent requires relatively high detergent concentrations, which can affect certain assays, especially immunoturbidimetric assays. In addition n-alkane sulphonate is an aggressive detergent that can inhibit the reaction of interest. This known agent therefor cannot give total clearing and optimum antibody-antigen reaction.
The object of the present invention is to provide an agent for the removal of turbidity that is particularly adapted for use with CRP assays, but can be used also with other assays.
An agent according to the invention comprises 0.5 to 10 mM phenol, 0.5 to 15% of a polyoxyethylated triglyceride, and 0.5 to 15% of at least one further non-ionic tenside. Preferably a combination of two further non-ionic tensides is included.